Patent Document 1 discloses a pre-warm-up operation control apparatus for an internal combustion engine, which controls the operation of the internal combustion engine until the completion of warm-up or until the temperature of the exhaust gas purification apparatus provided in the exhaust system of the internal combustion engine becomes equal to or higher than an active temperature. The pre-warm-up operation control apparatus controls the ignition timing in such a way that the ignition timing is retarded from normal ignition timing until the completion of warm-up is detected and keeps the increase rate of the intake air quantity equal to or lower than a predetermined value without regard to the operation of the accelerator.
Patent Document 2 discloses a combustion air-fuel ratio control apparatus for an internal combustion engine. When warm-up of an exhaust gas purification catalyst is requested, the combustion air-fuel ratio control apparatus makes the combustion air-fuel ratio in the combustion chamber rich and actuates a secondary air supply apparatus to supply secondary air to the exhaust passage. When warm-up of the exhaust gas purification catalyst is requested, the combustion air-fuel ratio control apparatus performs an open control to make the combustion air-fuel ratio equal to a first combustion air-fuel ratio at which stable combustion is possible between the theoretical air-fuel ratio and a combustion limit air-fuel ratio that is richer than the theoretical air-fuel ratio, if an exhaust air-fuel ratio sensor provided upstream of the exhaust gas purification catalyst is in an inactive condition. If the exhaust air-fuel ratio sensor is in an active condition, the combustion air-fuel ratio control apparatus performs a feedback control to make the combustion air fuel ratio equal to a second combustion air-fuel ratio that is richer than the aforementioned first air-fuel ratio and close to the combustion limit air-fuel ratio.